Is silk and steel strings safe for a nylon string classical guitar with truss rod?

It is not advisable to use silk and steel strings on a nylon string classical guitar with a truss rod. Silk and steel strings are typically used on acoustic steel-string guitars, while nylon strings are specifically designed for classical guitars. The tension of silk and steel strings is much higher than that of nylon strings, and can put excessive strain on the guitar's neck and truss rod, potentially damaging the instrument.

Furthermore, silk and steel strings are not designed for the specific tonal qualities of classical guitar music, which is characterized by its warm and mellow sound. Nylon strings are better suited for producing this traditional classical guitar timbre.

If you wish to use silk and steel strings on your nylon string classical guitar, it is highly recommended to consult with a professional guitar technician or luthier to assess whether your guitar's construction and truss rod can withstand the higher string tension. They can also make any necessary adjustments to ensure the safety and integrity of your instrument.